A Norfolk farmer has found an alternative use for his crop-spraying drone - whitewashing the glass roofs of greenhouses to protect plants in the hot weather.

Chris Eglington, who farms at Letton, near Shipdham, also runs technology firm Crop Angel.

He has been trying for years to win approval to spray chemicals from his customised aerial drone sprayer, as a more targeted way to control crop pests and diseases.

But while he is still not permitted to drop agro-chemicals from the air, a change to his updated licence means he can now apply online for permission to drop items such as seeds or water, which he has demonstrated at agricultural shows.

And it has created a new market for the technology - by allowing him to spray a 16:1 dilution of white paint onto horticultural greenhouses in Lincolnshire, which grow pot plants for a major supermarket.

Mr Eglington said it was faster and less dangerous than using human workers on fragile roofs.

"We cannot do chemicals, but we can do whitewash," he said.

"We did a trial, but a few days later I had an emergency call asking if there was any way we could come back and put the whitewash onto these greenhouses because the Health and Safety people said you cannot let men go up there, so you will have to find another way of doing it.

"I pulled out all the stops and we did two greenhouses in two days.

"Spraying greenhouses with whitewash has been done for a lot of years. You will see quite a few greenhouses with whitewash to slow down the penetration of the sun.

"It was getting too hot, even with the windows open. They had people working in there and in one particular glasshouse they were losing plants left right and centre. The plants were dying because there was too much heat.

"Obviously it is much safer than having men up there, and it is three times faster, so it does not disrupt the workflow of people working in the glasshouses."

Mr Eglington said he believes his firm will attract more enquiries for this service, but he "would rather franchise it to other people, provide the kit and let them get on with it".